1. Field of the Invention
The present invention relates to a high-voltage capacitor, a high-voltage capacitor device and a magnetron using this high-voltage capacitor device.
2. Description of the Related Art
As disclosed in Japanese patent application publication No. 8-78154, high-voltage capacitors of this type, which are incorporated into a magnetron as a filter to eliminate unwanted radiation waves generated by oscillation of the magnetron, generally comprise a high-voltage capacitor, through conductors (central conductors) and a grounding metal.
The high-voltage capacitor comprises a dielectric porcelain with two spaced through holes, two individual electrodes provided on one surface of the dielectric porcelain, and a common electrode provided on the other surface of the dielectric porcelain. The through conductors are disposed to pass through the through holes of the dielectric porcelain, and each through conductor is electrically and mechanically connected to each individual electrode. The grounding metal is electrically and mechanically connected to the common electrode and is electrically insulated from the through conductors.
In this type of high-voltage capacitor device, the cost of the dielectric porcelain makes up a large proportion of the total cost. The cost of the dielectric porcelain is proportional to its volume. In order to decrease the total cost, therefore, the dielectric porcelain is required to be reduced in volume for downsizing.
In the high-voltage capacitor of this type, however, the dielectric porcelain is formed with the two spaced through holes and the through conductors are disposed to pass through the through holes. This structure requires to keep a sufficient distance between the through holes to assure full voltage withstand performance between the through conductors, which sets a limit to reducing the size of the dielectric porcelain. Specifically, the size of the dielectric porcelain measured in an arrangement direction of the through hole is made up of a distance measured between centers of the through holes and twice a distance measured outwardly from the center of the through hole to the outer periphery of the dielectric porcelain. This sets a limit to the size reduction of the dielectric porcelain, and, consequently, to the cost reduction.
In addition, the dielectric porcelain having a relatively complex shape with the two spaced through holes tends to complicated structures of other components to be combined with this dielectric porcelain, such as an electrode connection metal to electrically and mechanically connect the through conductor to the individual electrode, a grounding metal to be electrically and mechanically connected to the common electrode of the high-voltage capacitor, an insulating cover for sheathing, and an insulating case.